The present invention generally relates to memory storage devices of the type that include one or more rotating discs. More particularly, the present invention concerns rotating disc memory storage devices that include a housing that provides a dust-free environment for the rotating disc or discs.
U.S. Pat. Nos. 4,280,155 and 4,282,554 are illustrative of that type of rotating disc memory storage apparatus known as fixed disc drives. As shown in the '554 patent, a fixed disc drive typically includes a housing made of two generally bowl-shaped casings that are fastened together to form an air-tight seal therebetween so that the discs are isolated from the ambient environment. Such air-tight seal is desirable because the presence of dust or other air-borne contaminants on the active portions of the discs will introduce noise into read-out therefrom and will also induce rapid wear of the transducers and disc surfaces. It is also noted that the motor of the disc drive devices include air-tight bearing seals to further reduce the possibility of dust contamination, and also a filter is incorporated in the internal ventilation or cooling system of the device (as illustrated in U.S. Pat. No. 4,282,554) to remove any contaminants from air recirculated within the housing.
The aforementioned U.S. Pat. No. 4,280,155 discloses a fixed disc drive that includes a flat rectangular base plate made of aluminum and a bowl-shaped cover made of plastic. A magnetic transducer head carriage and positioning assembly (referred to hereinafter as a transducer actuator assembly) is mounted to the base plate adjacent the periphery of the discs, with the transducers being mounted upon flexure arms that project outwardly form the actuator assembly. The motor for rotating the discs is mounted above the base plate within the housing.
A major shortcoming of prior known art memory storage devices relates to tilt of the axis of rotation of the discs relative to the path of movement of the transducers as a result of temperature distortions in the housing or base plate upon which the actuator assembly is mounted. Referring, for illustrative purposes, to the aforementioned U.S Pat. No. 4,280,155, it will be seen that the uppermost flexure arm and associated transducer is spaced about twice as far from the base plate as the lowermost flexure arm and transducer. If heat is unevenly distributed across the base plate, as may be produced by the internally mounted motor, the base plate will tend to distort as a result of such heat so that the spindle axis tilts relative to the actuator assembly. If any "tilt" is so induced, the uppermost transducers will be shifted from the desired track location on the uppermost disc. It is noted that even a minute amount of such radial shifting is unacceptable in a fixed disc drive intended for very high track density.